Process of manufacturing wall board



Aug. 16,1927.

5. c. CLARK PROCESS OF MANUFACTURING, WALL BOARD Filed Sept. 2 1 2 2 Sheets-Sheetl g s. c. CLARK PROCESS OF MANUFACTURING WALL BOARD Filed Sept 23, 1925 2 Sheets-SheetZ c'c' q a k s.

Patented Aug. 16, 1927.

UNITED STATES I PATENT OFFICE.

SIDNEY C. CLARK, 01 PORT CLINTON, OHIO, ASSIGNOR TO AMERICAN GYPSUM COM- PANY, OF PORT CLINTON, OHIO, A CORPORATION OF OHIO.

PROCESS OF MANUFACTURING WALL BOARD.

Application filed September 2a, 1925. Serial m. 57,997.

terial is usually aboutthree-eighthsof an inch in thickness and is put on the market in various widths from 32 to 48 inches, and

in lengths from 6 to 12 feet The most extensive use for wall board is the finishing of interior walls, and ordinarily takes the place of lathand plaster, being nailed directly to the studding or to firring strips, and the surface decorated The chief difficulty experienced in the use of wall board, is the concealin joints between the boards, especia ly where a decorative coating is applied directly to I the surface of the ard. Various expedients have been adopted to overcome this difficulty, such as wood panel strips, crack filler, and tape, but none of these are wholly satisfactory since it has been 'found to be practically im ossible to eliminate unevenness at the a utting edges of the board.

One of the chief causes for this condition is the extensive use of what is known as a covered edge type of wall board, in which the margins of the covering sheets are folded over the side edges to cover the plaster body. Experience has shown that the folding of the paper over the edges makes it practically impossible to roduce a perfectly square and true edge, rst because cannot be folded 'to a sharp corner an ondly, because in the process of manufacture it is diflicult, if not impossible, to control the materials so that the edges of the finished board are perfectly true.

It follows, therefore, that while the sealing or covering of the edge makes for a more substantially and durable productforshippaper ment and handling, this advantage is ofl'set by the unevenness of the ed es, sothat it is ordinarily impossible to. app y the board edge to edge with any degree of certainty that the joints will either e flush or the cracks uniform. In short, whatever merit which may be claimed for a covered edge'board, extends only to the protection afforded durof the sec-1 ing transit, but thereafter becomes a source of difiiculty, if not a practical disadvantage. With improvements in methods of shipment and intelligent handling of the product, it is conceived that an actual covering of the stucco at the edges is not as essential as once regarded, and therefore may be dis- Ipjensed with, for the sake of trueness of edge.

owever, it is deemed desirable to reinforce (as distinguished from covering) the edge of the board, both to revent cracking and disintegrating at the e ges during shipment, and to rovide a stronger edge through which nails may be driven.

I have therefore conceived a type of plas- 'ter or-wall board which is essentiallyca reinforced edge board, so that it will have ample marginal strength to withstand shipment,

and yet have uniformly true andeven edges,

so that a perfectly flushjoint will be made when the boards are applied edge to edge on a wall. 1

This process or method'of treatment will now be disclosed, with the aid of the accompanying drawings, in which I Figure 1 is a perspective view of a piece of plaster board. showin the preferred type of edge, prior to the nal process.

F gure 2 is a view similar to Figure 1, showing the finished 'product.

y Fi re 3 is a view in side elevation of a suita le apparatus for processing the board in accordance with the invention.

Figure 4 is a top plan view of the apparatus.

Figure 5 is an enlarged top lan view of one of thegrinding elements 0 the apparatus.

Figure '6 is an enlarged view in elevation of the grinding element as taken on line 66 of Figure 5, and v Figure 7 is an enlarged detail view showing the action of the grindingwheel on the Inn body of stucco 1, with the coverin sheets 2,

2, extending over the faces of t 'e stucco. The margins 2 of the coverin sheets are carried to the side edges of the ody, thence folded over the side or edge faces for a short it will be forced out between spread unevenly over the entire edge faces.

thickness of stucco between. Particularly is it diflicult, if not impossible, to secure a sharp bend either at the point where the paper s first folded over the edge or where it enters the body, in fact, the very nature of the aper is such that roundededges invariab y result. Moreover, it is often diflicult to control the flow of stucco between the folded in edges of the paper so that in some instances a groove will be formed and again the folds, and

The difliculty in controllingthe action of paper and stucco will be better understood from a brief description of the process of manufacture which with but slight departuresis common to the industry. For this reason it is not deemed necessary to disclose the structure of a laster board machine since the following escription will be well understood by those skilled in the art.

A plaster board machine consists primarily of a horizontal travelling belt. At the head end of the machine are located the paper and stucco feeding devices. The paper is fed continuously from rolls, so placed that one sheet is above the other as it passes between a pair of forming rolls spaced apart above and below the belt a distance equal to the thickness of the finished board. As the sheets travel toward the rolls, the stucco in a wet state is deposited onto the lower sheet and is spread to a uniform thickness as the paper and stucco pass through the rolls on the belt which is of such length as to give the stucco an opportunity to set before'it is cut to lengths and dried.

In forming a folded'or sealed ed e, such as disclosed in Figure 1 suitable fol ing devices or horns are use which are located just aheadof the forming rolls, and in the path of the margin of the travelling sheets. These folding horns are shaped so as to bend or turn the margins inwardlyas the stucco spreads between the folds. To prevent the stucco from spreading'beyond the edge and to form a square edge, side dams as they are called, are located in line with the edges of the board, and coact with the folding horns to square the edge of the board and to auge its width.

Owing to t e nature of the materials, which are in more or less unstable condition, it is a difficult matter to produce a perfectly square or uniform edge since, as before explained, the paper does not bend at a sharp angle, nor is it always possible to bend back sheets of paper along the same line. As a result therefore, the edge, which approximates a straight and square edge, may be slightly out of square, as one sheet will be more rounded than the other, any one of these variations occurring in a relatively short length of the product.

To remedy this, and at the same time at tain the desired results, it is proposed to subject the edges of the board to a grindmg process. This may be done either during or after themanufacturing process; that since the board is then hard and in bettercondition for grinding.

For the purpose of illustration an inclined section of delivery track isshown in Figure 1, along which the boards are advanced from the drying apparatus. Beyond the inclined section is a straight track section or extension.

The track sections are made of structural steel frame work, with parallel side frames 3 3, spaced apart at substantially the same distance as the boards extending transversely and at intervals are rollers 4 journalled at their ends in the side frame members.

Near the delivery end of the track are located grinding elements 55, consisting of grinding wheels 6-6, of a suitable abrasive material mounted directl on the'armature shaft of motors 7-7. hese grinding elements are accurately positioned .in transverse alignment with each other on opposite sides of the track, with the plane of the grinding wheels at right angles to the edges of the boards. In such position the periphcries of the wheel extend inwardly beyond the side frame members, and for this reason, portions as at 8-8, are cut away.

The details of the-grinding elements are clearly shown in Figures'6 and 7. The motors being fixed to a suitable bracket 9-9 adapted to have sliding connection with a beam or flanged cross member 10, extending beneath the rollers. In this way the grinding elements may be adjusted and set to the desired distance between the indin faces and thusgovern the final wi th of t e finished boards.

Figures 5 and 6 also show a length of plaster board A being advanced along the track and between the grinding wheels 6-6, the'latter being driven at arelatively high rate of s eed, and in a direction such that the grin ng cut is downward, although this is not essential. 'Figure'7 shows more clearly the nature of the grinding operation, the

advanced between the grinding wheels. It

is desirable that the wheels be ofrelatively large diameter not only to secure high peripheral speed, but alsoto reduce to a minimum the tendency of a hollow ground edge being formed. Moreover, it is important to set the grinding wheels so that the plane of the board coincides with a horizontal plane passing throu h the axis of the wheels, and thus avoids the grinding of the board to abeveled edge.

Assuming that the width of the finished board is 36 inches, the machine would be set so that the initial product is say, 36 4 inches. Thus, if the distance between the faces of the Wheels is set at 36 inches, it follows that of an inch of the material is removed from each edge of the board by the grinding wheels. The amount removed may vary, but it is the purpose to remove suflicient of the edge to include the thickness of the paper which extends over the face and a sufficient amount beyond so as to include the bends in the paper at the point where it folds over the edge as well as the point where it enters the stucco. In other words, it is the function of the grinding wheels to remove a substantial portion of the edge in cluding all of the paper at the edge, thuscompletely severing the embedded margins from the top and bottom, sheets, the same becoming strips 2 extending along the edges which serve to reinforce the stucco which is wholly exposed.

Moreover, any unevenness in the edge or slight variations in width is overcome with the result that the board leaves the oint of g'inding with a perfectly true an square e e;

It follows therefore that the process here in set forth departs from any thought of protecting the edge by a covering of paper, since any advantage that might be gained by the partial covering in the initial forming of the edge, is deliberately sacrificed in favor of what is considered. of greater importance, namely, a product of. uniform width and a erfectl true edge, together with a suitab e rein orcement the stucco from cracking, and to provide an edge throughwhich nails can be driven without injury to the board.

I consider the grinding process as the only practical method of obtaining the re to preventv sults set forth, inasmuch as cutting or trim- I ming the board by other means does not insure either the smoothness of surface or the degree of uniformity required for making a perfect joint.

Having set forth the process embodying the invention, I claim;

1. The process of manufacturing plaster board consisting of introducing stucco in its wet state between sheets of covering material, forming a composite material of predetermined thickness and of approximately predetermined width, and grinding the edges of the formed material to an exact predetermined width.

2. The processof manufacturing plaster board, consisting of introducing stucco in its wet state between sheets of covering material, folding the mar ins of one of said sheets over the edge of t e board and thence into the stucco, reducing the material to a predetermined thickness and passing the same between grinding wheels spaced apart at a predetermined distance to remove por-' tions at the edge of the board including the portions of the sheet covering the same.

3. A rocess of treating plaster board having e marginal portions of the covermg sheets folded over the edges and thence embedded in the plaster body, consistin of advancing the board between grin ing wheels, thereby removing the material at the edges to a depthsubstantially equal to the thickness of the marginal portions of said covering sheets.

4. The process of treating plaster board having a covered edge, consisting of advancing such board lengthwise between grinding wheels to remove the edge covermg and'a portion of the material adjacent thereto.

5. The process of finishing plaster board, initiall manufactured with a covered edge forme durin the process of manufacture by folding e mar 'ns of the covering sheets over the ed e o 1 the plaster body and thence into said ody between said cover sheets, consisting of advancing the boards. lengthwise between rotative grinding wheels acting simultaneously on opposite, side edges SIDNEY C. CLARK. 

